I would like to specify my question further :
1. What I mean "Li ion transport" is refer to a single ion behavior(not a statistical concept);
2. Both Chemical potential and concentration gradient should be terms describing a system;
2a. Is it possible for chemical potential to describe a solid state system while the internal energy and volume could change?
2b. What's the differences of chemical potential term in solid and liquid/gas?
3. Is there a build-in electric field in electrodes? To what extent it could influence ion transport compared with chemical potential?